1. Field of the Invention
This invention relates to abrasive articles, more particularly abrasive articles that comprise abrasive particles, a binder, and a grinding aid.
2. Discussion of the Art
Abrasive articles generally comprise abrasive grains secured within a binder. In a bonded abrasive, the binder bonds the abrasive grains together in a shaped mass. Typically, this shaped mass is in the form of a wheel and thus it is commonly referred to as a grinding wheel. In nonwoven abrasives, the binder bonds the abrasive grains to a lofty, open, fibrous substrate. In coated abrasives, the binder bonds the abrasive grains to a substrate or backing. Coated abrasives may comprise a first coated layer bonded to one side of the backing (commonly referred to as a make coating), at least one layer of abrasive grains bonded to the backing by the make coating, and a second coating layer overlaying the abrasive particles. The second coating layer commonly is referred to as a size coating; it reinforces the retention of the abrasive particles. Coated abrasives also may include an additional "supersize" coating overlaying the size coating. The supersize coating can include a grinding aid, which in some instances is beneficial during grinding.
Abrasive binders typically consist of a glutinous or resinous adhesive, and, optionally, additional ingredients. Examples of resinous adhesives include phenolic resins, epoxy resins, urethane resins, acrylate resins and ureaformaldehyde resins. Examples of typical additives include grinding aids, fillers, wetting agents, surfactants, pigments, coupling agents, and dyes.
The addition of grinding aids can significantly affect the chemical and physical processes of abrading metals to bring about improved performance. It is believed that grinding aids either (1) decrease the friction between the abrasive grains and the workpiece being abraded, (2) prevent the abrasive grains from "capping", i.e., prevent metal particles from becoming welded to the tops of the abrasive grains, (3) decrease the interface temperature between the abrasive grains and the workpiece, and/or (4) decrease the required grinding force. Grinding aids are particularly beneficial during the abrading of metals such as stainless steel or titanium. In some instances, the addition of a grinding aid can significantly improve the cut rate or abrading properties of the resulting coated abrasive over a coated abrasive that does not contain a grinding aid. The abrasive industry is always looking for ways to improve the efficiency of abrasive products through the use of grinding aids.
In some instances, the grinding aid and abrasive binder are not compatible. This incompatibility can lead to problems during processing and ultimately decrease performance. Thus, the abrasive industry is looking at ways to further optimize existing grinding aids.